Nationals beat writer Adam Kilgore talks about whether Ryan Zimmerman will eventually return to third base when he rejoins the team. (Post Sports Live/The Washington Post)

For the first time since the seventh inning of the season opener March 31, a span of 80 games over three months, the Washington Nationals are whole again. Outfielder Bryce Harper is expected to rejoin the Nationals on Monday in Washington after missing two months. But now a difficult conundrum, discussed for weeks, rests in the hands of first-year Manager Matt Williams: Where will everyone play and how often?

Williams has outlined several scenarios: Harper can play all three outfield positions. Ryan Zimmerman can play his newer positions of left field and first base and even return to his old one at third. Anthony Rendon, who has played well at third while Zimmerman was hurt and then in left, can jump between second and third. But in several of those combinations, established everyday players would have to sit.

“I don’t view it negatively,” Williams said. “I view it positively in that those are tough decisions to make but it’s great if you have too many guys and you have all these guys who are everyday players.”

Over the weekend, Williams admitted he has a specific plan in mind but declined to share it. But his words and actions offered some clues. He hinted that managing the egos of regular players sitting wouldn’t be as difficult as expected, suggesting there wouldn’t be unexpected overhaul. And considering the state of the offense — 20th in runs scored per game at 4.0 — Williams perhaps will opt for the best offensive lineup possible.

“There’ll be some creative things that Matt is going to have to do to figure out where everybody is playing,” first baseman Adam LaRoche said. “ . . . He’s our boss, and we’ll listen to him. We’ll see what happens.”

Williams said he will make daily adjustments based on several factors: creating advantageous matchups and resting players. Two lineup mainstays — right fielder Jayson Werth and LaRoche — are 35 and 34, the oldest position players on the team, and Williams is keeping their long-term health, as well as their teammates’, in mind.

“Everybody wants to play every day, but physically it’s demanding,” he said. “And where we’re at right now, we have to look at history. We have to look at where we’re at now and how we got here. We got here by running a pretty regular lineup out there every day. To do that for the course of 162 is probably not a smart thing, so we want to give guys some days [off].”

During his rehab assignment, Harper played all three outfield positions. Harper has played left field primarily since 2013; he has said he prefers center field but will play where needed. If Werth were given rest, Harper could play right field. Williams said he would talk with Harper when he returns about the team’s plans and needs.

“He’s a great athlete,” Williams said. “He can play anywhere.”

Under certain potential scenarios, Harper could spell everyday center fielder Denard Span or Werth, who has started 77 of 81 games. Werth said he is open to resting when Harper returns, but after that, he expects to be in the lineup every day.

“Doesn’t really matter if I am or I am not” open to rest after that, Werth said. “This is a team. You can go in and politic for yourself, but at the end of the day it’s, you know, ‘He who holds the ball controls the game’ but more like ‘He who holds the pen controls the lineup.’ ”

Span has manned center field and led off nearly every day since 2013 but could rest more often under Williams’s plan. If Zimmerman were to play left field, perhaps Harper could man center instead of Span. Span’s on-base percentage has declined in recent years but he still provides extra-base hits. He is hitting .268 with a .705 OPS. His slugging percentage (.392) is higher than Werth’s (.374) this season, and Span provides brilliant defense.

“There’s no question it’s going to be a tough decision for him,” Span said Saturday. “I don’t know. I haven’t talked to [Williams]. I don’t know what’s going to happen. At the end of the day, I want to help this ballclub. If you ask me personally, I feel like I’m best used playing every day. If that’s not the case, I’ll do whatever when my number is called and be ready.”

The outfield logjam could be solved on many days if Zimmerman returns to third base. Williams has maintained for weeks that Zimmerman could return there this week. Zimmerman has taken grounders at third twice this past week, including last Monday for the first time since he returned June 3 from a broken thumb.

The infield defense may suffer — Zimmerman has committed 30 throwing errors at third base since 2012, and his surgically repaired shoulder flared up again this season — but his ability to play third base again may give the Nationals the best offensive lineup. The ripple effect: Rendon would play second, and Danny Espinosa would head to the bench. Zimmerman also could spell LaRoche at first base against tough left-handed pitchers.

Zimmerman will “play all over,” Williams said. “He’ll play some first, some left, third certainly. That’s the plan going forward. It’s going to be a daily thing.”

Although Zimmerman has said he enjoys left field and his past comments about third sound like a goodbye, he is willing to do what is needed.

“The goal is to win, and if that gives us the best chance to win, that’s what I’ll do,” he said.

The Nationals could return to a scenario in which Espinosa plays but Rendon is the primary second baseman again. Espinosa had a strong first month but is hitting .217 with a .632 OPS and is 0 for his past 18. He provides power and Gold Glove-quality defense at second — which, as a ripple effect, boosts the infield defense as a whole. But Espinosa is striking out nearly 35 percent of his plate appearances, a career-high rate.

Williams had the chance to start Espinosa in Saturday’s doubleheader but used Kevin Frandsen at second in both games. Williams explained he wanted Frandsen’s bat in the lineup because of his past experience against the Cubs’ second game starter, Jeff Samardzija, but Espinosa had moderate success in limited chances against him, too. Rendon playing second base again could solve the lack of production from that position. Although Rendon is more comfortable at third base and played well there, he is also willing to do what is asked.

“From last year and all of spring training, I’ve learned how to play second base and building [comfort] there, he said. “I knew there was a chance I’d be [jumping around] throughout the whole season, switching back and forth. I’m prepared to go in at second. I just want to hit.”

The next few weeks will be a fascinating test for Williams. Any given day could bring a different defensive alignment and lineup. But for the Nationals, the most promising development will be a healthy team again.

“We’re all waiting for that moment,” said catcher Wilson Ramos, who returned from his second stint on the disabled list last week. “Having everyone healthy, it’s something we all want. With Bryce back, I hope we all stay healthy for the rest of the season. We’ll have the entire team here, and as a result, I think a lot of good will come. It’ll be a fun final three months.”